This invention relates to a power storage system for electric railway which is connected to a power system for supplying the electric vehicles of the electric railway with electric power and in which a motor-generator and a flywheel are coupled.
Regarding the installation of the system of the type specified above, as illustrated in FIG. 1, there have heretofore been proposed (a) a case where a power storage apparatus 3a for electric vehicles is located along, with or near a power substation 2A, which is indicated as a substation for rectifying commercial A.C. power into D.C. power, (b) a case where a power storage apparatus 3b is located midway between a power substation 2A and a power substation 2B, and (c) a case where, instead of a power substation 2B, a power storage apparatus 3c is located, at the tail end of an overhead trolley line 1 which constitutes the power system. Actually, measures intermediate between the cases (a), (b) and (c) and arrangements with the cases combined are also performed. The power storage apparatus is constructed of a motor-generator 4, and a fly wheel 5 and a controller 6 which are coupled to the motor-generator. Numeral 7 designates an electric vehicle or train which is running.
Electric cars controlled by, e.g., choppers have been widely used in recent years to the end of reducing power consumption in the electric vehicles, and they have the feature of being capable of power regeneration during braking. The operation of the power storage apparatus of the specified type is sometimes intended for the storage of the regenerative power, and sometimes for the so-called "peak cut " for relieving the influence of high power on the substation, the high power being usually required during the starting or acceleration of the electric vehicles. These modes can be selected by controlling the motor-generator. Anyway, the reduction of losses attributed to the operation of the power storage apparatus is a technical problem, and various solutions have been studied and proposed. The conventional methods of reducing the losses, however, are still countermeasures on the power storage apparatus itself.
More specifically, the losses attendant upon the rotation of the flywheel 5 are principally a loss ascribable to frictional resistance with the ambient air and a loss ascribable to the friction of contact between the flywheel body and a lubricant or metal in a bearing suspending the former. In order to lighten the losses, according to the countermeasures, the apparatus is deaerated into vacuum, and the bearing is made small in size so as to reduce the bearing loss, the insufficient component of the load capacity of the bearing being supported by a magnetic bearing or the like which causes no loss. Enhancing the performance of the flywheel 5 itself can also be deemed an important measure for the loss reduction. All the above proposals, however, are technical measures within the power storage apparatus itself. It is the present situation that any attempt to reduce the losses from the viewpoints of the operation of the power storage apparatus and the service of the electric railway has not been proposed yet.